A bag-type dust collector is often used to collect and filter dust in the air to maintain the air quality of the environment. The bag-type dust collector comprises a machine stand. The machine stand is provided with an air bellows. One end of the air bellows is provided with an air inlet. The bottom of the air bellows is provided with two first air outlets. The top of the air bellows is provided with a plurality of second air outlets corresponding to the first air outlets. An air blower is provided, corresponding in position to the air inlet. The first air outlet is provided with a dust collecting bag. A fastening ring is provided on the outer peripheral side of the first air outlet. The dust collecting bag is tightened by the fastening ring so that the dust collecting bag is fixed to the first air outlet. The second air outlets are provided with a plurality of filter bags, respectively. The filter bags can be used to filter the dust in the air, so that when the air blower is activated, the air with dust in the environment is sucked from the air inlet to the air bellows. Through the inertia and gravity, the heavy dust falls to the dust collecting bag, the light dust flows along with the air flow to the filter bags to be adsorbed to the filter bags, and the air is returned to the environment through the filter bags.
After a period of time, the dust collecting bag needs to be cleaned or replaced due to dust accumulation. Therefore, when the user wants to replace the dust collecting bag, the fastening ring is loosened to disengage the dust collecting bag from the first air outlet for replacing the dust collecting bag. A clean dust collecting bag is fitted to the first air outlet, and then the fastening ring is fitted to the first air outlet and the dust collecting bag. Finally, the fastening ring is tightened to secure the dust collecting bag. However, the dust collecting bag must be tightly fitted to the first air outlet. The user often spends a lot of time and needs a sufficient space to replace the dust collecting bag. The replacement of the dust collecting bag is complicated, resulting in inconvenience to the user. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.